As vehicles become more complex, vehicle designers change more and more parameters to modify performance and improve safety. One parameter that may be modified to change performance is the pressure within the tires of the vehicle. Unintended changes in the pressure within the tires of the vehicle may cause unwanted performance variations. These performance variations may include not only fuel consumption variations, but also safety concerns. Several efforts have been made to allow monitoring of the pressure in vehicle tires. In addition to merely monitoring the pressure in the tires, there is also a need to communicate the data from the monitoring to a location where the information may be used.
Because of the rotation of the tires, wire-based solutions to the communication issue are impractical. The pressure monitor is typically positioned on, and often inside, the tire itself such that the rotation of the tire precludes a wire-based communication link. Wireless solutions do offer many advantages and several systems have been proposed. In a typical solution, a transponder may be positioned within the vehicle and coupled to a pressure sensing device. An interrogator wirelessly queries the transponder and the transponder replies with information derived from the pressure sensor.
Because of differing vehicle designs, it is advantageous to have differing transponder designs. Having more transponder designs allows designers more options when integrating the transponders into vehicles and better designs may be the end result. To date, there has been a shortage of teachings in ways to distribute the interrogator within a vehicle. Likewise, how the transponder responds is a parameter of the sensing system that may be changed depending on the needs of the interrogator. Thus, providing a dual or multi-mode transponder may provide benefits to the designer.